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Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces. [1] Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with other positively charged particles in the surrounding soil water. [ 2 ]
Laboratory tests used to diagnose a soil as dispersive focus on the cation exchange capacity of a soil sample and its cation breakdown. Soil cations are dominated by Ca 2+, Mg 2+, K +, and Na +, as well as H + in acidic soils. The exchangeable sodium percentage ( "ESP", (sodium / (total cations)) * 100 ) is a key indicator derived from these ...
CEC is the amount of exchangeable hydrogen cations (H +) that will combine with 100 grams dry weight of soil and whose measure is one milliequivalent per 100 grams of soil (1 meq/100 g). Hydrogen ions have a single charge and one-thousandth of a gram of hydrogen ions per 100 grams dry soil gives a measure of one milliequivalent of hydrogen ion.
Humus is a negatively charged colloidal substance which increases the cation-exchange capacity of soil, hence its ability to store nutrients by chelation. [62] While these nutrient cations are available to plants, they are held in the soil and prevented from being leached by rain or irrigation. [52]
The term "sodic soil" is sometimes used imprecisely in scholarship. It's been used interchangeably with the term alkali soil, which is used in two meanings: 1) a soil with a pH greater than 8.2, 2) soil with an exchangeable sodium content above 15% of exchange capacity. The term "alkali soil" is often, but not always, used for soils that meet ...
Nutrient cations, including potassium and many micronutrients, are held in relatively strong bonds with the negatively charged portions of the soil in a process known as cation exchange. Phosphorus is a primary factor of soil fertility as it is an element of plant nutrients in the soil.
The main processes of soil formation of oxisols are weathering, humification and pedoturbation due to animals. These processes produce the characteristic soil profile.They are defined as soils containing at all depths no more than ten percent weatherable minerals, and low cation exchange capacity.
Where urea is made available cheaply to farmers, it is also used to reduce the soil alkalinity / salinity primarily. [11] The ammonium (NH + 4) cation produced by urea hydrolysis which is a strongly sorbing cation exchanges with the weakly sorbing Na + cation from the soil structure and Na + is released into water. Thus alkali soils adsorb ...